The present invention relates to a method and an apparatus for measuring the thickness of a film on a substrate, and a substrate processing apparatus utilizing the same. The method and apparatuses of the present invention can be advantageously employed especially in effecting real-time detection and monitoring of a film thickness of a substrate on a side being processed during processing. It should be noted that “measurement of a film thickness of a substrate” in the present invention means not only measurement of a film thickness of a substrate, but also detection or observation of a condition of the substrate, such as the presence or absence of a metallic thin film formed on the substrate.
As a conventional technique of the above-mentioned type, Unexamined Japanese Patent Application Public Disclosure (Kokai) No. 7-251371 discloses the technique of emitting light from a distal end of a glass fiber to a measurement surface of a substrate during polishing, and receiving the light reflected by the measurement surface through the glass fiber. The glass fiber guides the reflected light to a film thickness measurement control unit.
In the above-mentioned technique of emitting and receiving light through a glass fiber, a measurement error is likely to occur due to the presence of drops of liquid formed on the substrate during polishing. Further, it is required to strictly control the distance between the distal end of the glass fiber and the measurement surface of the substrate.
Unexamined Japanese Patent Application Public Disclosure (Kokai) No. 10-264017 discloses the technique of placing a polished substrate in a cleaning liquid in a cleaning tank, inserting. a distal end of an optical fiber into the cleaning liquid and bringing it to a position in the vicinity of a measurement surface of a substrate. Those steps are followed by emitting light to the measurement surface, and introducing the light reflected by the measurement surface through the optical fiber to a film thickness detection apparatus.
In the above-mentioned method of placing the distal end of the optical fiber in the cleaning liquid, it is necessary to control the distance between the distal end of the optical fiber and the measurement surface of the substrate. Further, a large apparatus is required.